1. Field of the Invention
The present invention generally relates to electronic musical instruments and, more particularly, to an electronic musical instrument such as electronic pianos or the like in which a resonance sound is generated by operating devices such as keyboard, pedal and so on.
2. Description of the Related Art
A pedal effect addition has been widely performed in electronic pianos in order to add similar effects as those of a sustain pedal of an acoustic piano. According to a known pedal effect adding system, when the pedal is stepped, a sound is generated so as to have the same musical sound envelope as that brought by continuously pushing the key even after the key is released. Another proposal has also been made, in which the envelope characteristic is switched in response to the on and/or off state of the pedal. Further, in such proposal it is also known that the envelope characteristic is switched in response to the continuous displacement of the stepped amount of the pedal.
Furthermore, considering the function of the pedal in the acoustic piano, it is to be noted that the important constituent of a particular sound generated when the pianist steps on the pedal is not only formed of the sound brought by the change of envelope characteristic but also of a resonance sound generated by resonating other strings by the vibration of a string of a pushed key when damper of all strings are released. From this standpoint, such a technique is proposed that a reverberation effect is added to musical sound generated in response to the operation of the pedal so as to generate the above resonance sound in the electronic musical instrument in a false fashion.
According to the above technology, the effect of the resonance sound can be added to the musical sound with ease.
In the acoustic piano, the fluctuation or undulation are generated in the resonance sound due to the fact that the string is tuned on the basis of a characteristic called a tuning curve and due to a shift of overtone frequency caused by the size of the string itself.
However, there is then the disadvantage that fluctuation undulation effects of the resonance sound cannot be achieved without difficulty only by the addition of reverberation effect like the above example of the prior art.
Further, the sound volume of the resonance sound of the above-mentioned acoustic piano is different depending on the key note of the pushed key because the sound volume of the resonance sound depends upon the number of other strings having overtone component close to a fundamental tone or overtone of the string of the pushed key. It is considered that, if the key note of the pushed key is high, then the sound volume of the resonance sound becomes large.
However, there is then the disadvantage that resonance sounds whose sound volumes are changed in response to the key notes of the pushed keys cannot be generated only by the addition of the reverberation effect like the above example of the prior art.